PROJECT 1: The broad, long-term objectives of this research plan are to develop an integrated optical molecular imaging strategy that uses fluorescence peptides as probes to target the presence of premalignant (dysplastic) tissue in vivo. Macroscopic and microscopic fluorescence instruments are developed as complementary imaging methods for peptide detection. This methodology can be used for monitoring biomarker expression in small animal models and for the early detection of cancer in human patients undergoing screening. In this application, the colonic adenoma is used as a model for dysplasia. The specific aims are to 1) identify 5 candidate peptides using techniques of phage display for biopanning against cultured cells and freshly excised specimens of human colonic mucosa, 2) develop new optical imaging instrumentation using the dual axes confocal architecture to visualize the tissue microarchitecture relevant to peptide binding, and 3) validate preferential peptide binding to dysplasia in vivo in a genetically engineered mouse that forms polyps in the distal colon by somatic activation of Cre-recombinase and in human subjects undergoing routine screening colonoscopy. Peptides are chosen for development as probes because their high diversity and small size can provide high affinity binding with deep tissue penetration, and their low risk of immunogenicity and toxicity facilitate translation for use in the clinic. Phage display is a powerful combinatorial technique that provides an unbiased approach for identifying unique peptides that exhibit affinity binding to dysplastic mucosa as is well suited to accommodate subtle changes associated with the in vivo microenvironment. The dual axes confocal architecture provides an instrument that can achieve sub-cellular resolution with long working distance and overcomes the effects of tissue scattering using off-axis fluorescence collection. Moreover, this design can be scaled down in size for endoscope compatibility. A 5 mm diameter instrument package is sufficiently small to pass through a 6 mm diameter instrument channel in a therapeutic endoscope. High speed scanning is performed with a tiny MEMS (micro-electro-mechanical systems) mirror that collects optical sections at a sufficient frame rate for generating 3D volumetric images. The candidate peptides will be topically applied to colonic adenomas and surrounding normal appearing mucosa followed by macroscopic fluorescence imaging to localize regions of increased peptide binding for subsequent microscopic fluorescence imaging to assess the spatial distribution of peptide binding within the dysplastic crypt microarchitecture. Public Health: The proposed studies will result in the development of novel optical imaging probes and instruments that can be evaluated in pre-clinical models as well as translated to the clinic as practical screening tool for the early detection of cancer in hollow organs.